Computing devices, cell phones and other electronic devices can store personal, private, and valuable information that a user of the device would like to keep secure. Current methods of securing access to the operation and contents of an electronic device include the user entering a personal identification number (PIN), the user entering a password, the user making a particular gesture upon a touch screen, such as a swipe motion, and a user pressing a fingertip into a fingerprint sensor. PINs and passwords (collectively, “access keys”) require that the user remember the access key and enter the access key to access the electronic device. It is well-known that a longer and more random access key offers better security than a shorter or more easily-guessed access key. However, long and random access keys are hard to remember and inconvenient to enter. Further, it is more likely that a user will make an error entering a long access key than a shorter one, thus requiring that the user re-enter the access key. Biometric sensors, such as fingerprint sensors, have been used to overcome some of the problems associated with using a long access key to secure an electronic device. However, fingerprint scanning is not deterministic as is a manually-entered access key. A fingerprint sensor scans a fingerprint and generates a sensor signal representing the fingerprint. The sensor signal is subjected to signal processing techniques including removal of signal artifacts in the sensor signal, normalization of the sensor signal, extracting of a set of features from the sensor signal that represent the fingerprint, and creating and storing a template of features to represent the fingerprint. Thus, the signal processing of a scanned fingerprint results in an approximation of the fingerprint signal data, not in an exact fingerprint image. A fingerprint scanning system must determine whether a scanned fingerprint sufficiently matches the stored approximation of the fingerprint signal data to permit access to the functionality and data of the electronic device. In addition, since the stored template of features are an approximation of the fingerprint of the user, a fingerprint system may have false acceptances of a fingerprint that is not the user's and may also have false rejections of a fingerprint that is the fingerprint of the user. Further, a human finger may leave a detectable image of the user's fingerprint on the fingerprint sensor or other objects. The detectable image can be recovered and used by another to gain unauthorized access the user's electronic device. A fingerprint, or other biometric identification scheme, also limits the utility of the electronic device by requiring the physical presence of the authorized user of the electronic device to provide the biometric information required to access the electronic device. For example, a user of an electronic device would not be able to lend her electronic device temporarily to a person whom the user trusts because access to the electronic device is limited by the user's biometric identification, requiring the presence of the user to access the electronic device. Alternatively, the user would have to give her PIN or password to the person to whom she lends the electronic device so that the person could access and utilize the electronic device. But, giving the person borrowing the electronic device the user's PIN or password would then give full access to the functionality and data of the electronic device to the person borrowing the electronic device, causing a privacy and security risk to the owner of the electronic device.